Debromination of the Flame Retardant Decabromodiphenyl Ether by Juvenile Carp (<i>Cyprinus carpio</i>) following Dietary Exposure

TLDR

BDE 209, the main component of decaBDE flame retardants that dominate the PBDE market, is highly hydrophobic (log Kow ≈ 10) and is thought to have low bioavailability, though fish may debrominate it to more bioavailable metabolites. Juvenile carp were fed BDE 209‑enriched food daily for 60 days followed by a 40‑day depuration, during which debrominated metabolites (penta‑ to octaBDEs) were identified by GC/ECNI‑MS and GC/HRMS and structurally inferred from retention‑time estimates. The study found no net accumulation of BDE 209, yet seven lower‑brominated metabolites accumulated in fish and liver tissues, indicating limited bioavailability of BDE 209 as debrominated products.

Abstract

The congener 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE 209) is the primary component in a commonly used flame retardant known as decaBDE. This flame retardant constitutes approximately 80% of the world market demand for polybrominated diphenyl ethers (PBDEs). Because this compound is very hydrophobic (log Kow ∼ 10), it has been suggested that BDE 209 has very low bioavailability, although debromination to more bioavailable metabolites has also been suggested to occur in fish tis- sues. In the present study, juvenile carp were exposed to BDE 209 amended food on a daily basis for 60 days, fol- lowed by a 40-day depuration period in which the fate of BDE 209 was monitored in whole fish and liver tissues sepa- rately. No net accumulation of BDE 209 was observed throughout the experiment despite an exposure concentration of 940 ng/day/fish. However, seven apparent debrominated products of BDE 209 accumulated in whole fish and liver tissues over the exposure period. These debrominated metabolites of BDE 209 were identified as penta- to octaBDEs using both GC/ECNI-MS and GC/HRMS. Using estimation methods for relative retention times of phenyl substitution patterns, we have identified possible structures for the hexa- and heptabromodiphenyl ethers identified in the carp tissues. Although exposure of carp to BDE 209 did not result in the accumulation of BDE 209 in carp tissues, our results indicate evidence of limited BDE 209 bioavailability from food in the form of lower brominated metabolites.